I fireform many calibres with cream-of-wheat using 700x powder
From PPC to 300 Win Mag,,,22BR, 22-250AI. 243AI, 25-06, 7mmSTW
Starting low I increase powder amounts until my case if formed and display sharp shoulders (rounded shoulders need more powder)
If your fired round has black powder coating the outside of the case then you need to add more powder.
I put the powder into the case, then add creak of wheat dry cereal to the top of the case mouth, then pack the wheat gently and firmly using an alan wrench that fits the inside neck. Then I stuff a ball of dacron fibre into the neck using the alan srench. Then I use scissors the hsircut any of the dacron hairs that stickup above the case mouth.
I have NEVER had a misfire or negative results.
Work up in 1 gr incriments (very fast powder)
Don't shoulder the rifle, and let the barrel cool.
"I shoot in the backyard of a populated area into an augered hole in the ground." ....very safe and very quiet
pic > 243AI brass being formed
Lots of fun